Thin film magnetic head with increased ariel density

ABSTRACT

A gap film of a write element is provided between a first pole portion and a second pole portion. The second hole portion includes a third magnetic film and a fourth magnetic film. The third magnetic film is provided adjacent to the gap film and the fourth magnetic film is provided adjacent to the third magnetic film. The surface of the fourth magnetic film facing opposite the medium includes a first side adjacent to the third magnetic film and a second sides extending outward from the first side. The second sides inclines toward the opposite side from the third magnetic film at an angle of less than 90° relative to an extended line of the first side to eliminate recording bleed occurring due to leaked magnetic field.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thin film magnetic head, andmore particularly to a combined type thin film magnetic head having astructure that exhibits improved areal density.

[0003] 2. Discussion of Background

[0004] Most thin film magnetic heads employed in magnetic disk devicesconstituting computer storage apparatuses at present are the combinedtype that are provided with a thin film write element and amagnetoresistive (MR) read element. MR read elements, which are notdependent upon the speed relative to the magnetic disk, are capable ofachieving a high degree of resolution. An MR read element includes afirst shield film, a second shield film and an MR element. The firstshield film and the second shield film are provided over a distance fromeach other via an appropriate non-magnetic insulator and the MR elementis provided between the first shield film and the second shield film.

[0005] The write element, which is constituted of an inductiveelectromagnetic transducer, is laminated on the MR read element. Aninductive thin film magnetic transducer to constitute the write elementis provided with a first magnetic film which also functions as thesecond shield film for the MR read element, a second yoke, a gap filmand a coil film supported by an insulating film and the like.

[0006] The front ends of the first magnetic film and the second yoke arerespectively constituted of a first pole tip and a second pole tip thatface opposite each other over the gap film having a very smallthickness, and write operation is performed at the first and second poletips. The first magnetic film and a second magnetic film are linked witheach other so that their yokes complete a magnetic circuit at a back gapportion located on the opposite side from the first and second poletips. The coil film is formed winding around the linking area of theyokes in a coil.

[0007] In order to support high recording density using this type ofthin film magnetic head, the quantity of data stored per unit area ofthe magnetic disk (areal density) must be increased. An improvement inthe areal density is achieved by improving the performance of themagnetic recording medium such as a magnetic disk and increasing thefrequency at the write circuit as well as by improving the capability ofthe write element.

[0008] In one of the means for increasing the areal density by improvingthe capability of the write element, the gap length between the poletips is reduced. However, since a reduction of the gap length leads to areduction in the recording magnetic field intensity between the poletips, there is naturally a limit to the degree to which the gap lengthcan be reduced.

[0009] In another means for increasing the areal density, the number ofdata tracks that can be recorded at the magnetic disk is increased. Thenumber of tracks that can be recorded at a magnetic disk is normallyexpressed as TPI (tracks per inch). The TPI capability of a writeelement may be enhanced by reducing the size of the head that determinesthe width of the data tracks. The head size is normally referred to asthe head track width.

[0010] In the case of a conventional thin film magnetic head in theprior art described above, since the first magnetic film at the writeelement is also employed as the second shield film of the MR readelement, the width of the first pole portion cannot be reduced, andconsequently, a rather large side fringing magnetic field is generatedduring a recording operation. This magnetic field is caused by a leak ofmagnetic flux from the second pole tip whose width is reduced to thefirst magnetic film whose width is not reduced. Such a side fringingmagnetic field restricts the lower limit of width that can be achievedand limits the degree to which the track density can be improved. Inaddition, it degrades the off-track performance when track data thathave been written are read by the MR element.

[0011] As a means for eliminating the problem discussed above, JapaneseUnexamined Patent Publication No. 262519/1995 and Japanese UnexaminedPatent Publication No. 225917/1995 disclose a means for adjusting thewidth of the lower portion to the width of the second pole tip throughion beam milling.

[0012] In addition, U.S. Pat. No. 5,600,519 discloses a structureprovided with a tapered portion between the zero throat point and anexpanded portion at the first magnetic film and the second magneticfilm.

[0013] Furthermore, U.S. Pat. No. 5,452,164 discloses a structureachieved by setting the width of the second yoke larger than the widthof the second pole tip so that the two side surfaces of the second yokein the widthwise direction project out from the two side surfaces of thesecond pole tip.

[0014] However, when the two side surfaces of the second yoke in itswidthwise direction are made to project out from the two side surfacesof the second pole tip by setting the width of the second yoke largerthan the width of the second pole tip, the magnetic field leakingthrough the edges of the pole tip in the widthwise direction increasesto result in recording bleed due to the leaked magnetic field.

SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide a separatetype thin film magnetic head in which the yokes and the poles areseparated.

[0016] It is a further object of the present invention to provide a thinfilm magnetic head with which recording bleed occurring due to leakedmagnetic field is eliminated.

[0017] In order to achieve the objects described above, the thin filmmagnetic head according to the present invention is provided with atleast one write element. In the write element, which includes a firstpole portion, a second pole portion and a gap film, the gap film isprovided between the first pole portion and the second pole portion. Thesecond pole portion includes a third magnetic film which is providedadjacent to the gap film. Consequently, by using the third magnetic filmas a pole tip and setting the head size that determines the width of thedata tracks to very small dimensions determined by the width of thethird magnetic film to improve the TPI capability, high densityrecording is achieved.

[0018] A fourth magnetic film included in the second pole portion isprovided adjacent to the third magnetic film. By using the fourthmagnetic film as a yoke, the magnetic flux which is required for a writeoperation can be supplied to the third magnetic film constituting thepole tip from the fourth magnetic film. In other words, according to thepresent invention, a separate type thin film magnetic head in which thepole tip is separated from the yoke can be achieved.

[0019] According to the present invention, the surface of the fourthmagnetic film facing opposite the medium includes a first side which isadjacent to the third magnetic film and second sides which extendoutward from at least one end of the first side. Each second sideinclines toward the opposite side of the third magnetic film at an angleless than 90° relative to an extended line of the first side. Throughthis structure, any recording bleed occurring due to the leaked magneticfield generated through the edges of the fourth magnetic film can beeliminated.

[0020] In the thin film magnetic head according to the presentinvention, the second sides are normally provided at the two ends of thefirst side. The second sides should preferably incline at an angle equalto or greater than 45°.

[0021] According to the present invention, since the surface of thefourth magnetic film facing opposite the medium includes the secondsides extending outward from at least one end of the first side, thewidth of the surface of the fourth magnetic film facing opposite themedium is set larger than the width of the surface of the third magneticfilm facing opposite the medium, resulting in the fourth magnetic filmprojected out toward the outside relative to the third magnetic film atthe two sides in the widthwise direction.

[0022] It is desirable that in the thin film magnetic head according tothe present invention, the first pole portion include a first magneticfilm and a second magnetic film. The second magnetic film is providedadjacent to the gap film, whereas the first magnetic film is providedadjacent to the second magnetic film. By combining this structure forthe first pole portion and the structure of the second pole portiondescribed earlier, a structure which is achieved by providing the firstmagnetic film, the second magnetic film, the gap film, the thirdmagnetic film and the fourth magnetic film adjacent to each other inthis order is realized. By adopting this structure, in which the secondmagnetic film and the third magnetic film among the four magnetic films,i.e., the first magnetic film to the fourth magnetic film, are employedas pole tips, the head size which determines the width of the datatracks can be set very small, determined by the widths of the secondmagnetic film and the third magnetic film to increase the TPI capabilityso that high density recording can be achieved.

[0023] In addition, the first magnetic film and the fourth magnetic filmmay be extended toward the rear from the pole portions to constituteyokes with the portions extended toward the rear. In this structure, amagnetic flux sufficient for a write operation is supplied from thefirst magnetic film and the fourth magnetic film constituting the yokesto the second magnetic film and the third magnetic film constituting thepole tips.

[0024] The thin film magnetic head according to the present inventionnormally includes an MR read element. In the MR read element, whichincludes a first shield film, a second shield film and an MR element,the first shield film and the second shield film are provided over adistance from each other with the MR element located between the firstshield film and the second shield film. The write element is laminatedon the MR read element. In this structure, the second shield film alsofunctions as the first magnetic film of the write element to achieve areduction in thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other objects, structural features and advantages of the presentinvention are explained in further detail by referring to the attacheddrawings illustrating preferred embodiments of the present invention.

[0026]FIG. 1 is a sectional view of the thin film magnetic headaccording to the present invention;

[0027]FIG. 2 is an enlarged perspective of the pole portion of the thinfilm magnetic head illustrated in FIG. 1;

[0028]FIG. 3 is an enlarged frontal view of the pole portion illustratedin FIG. 1;

[0029]FIG. 4 is a graph illustrating the relationship between theposition X (μm) and the leaked magnetic field Hx (k0e);

[0030]FIG. 5 illustrates another embodiment of the pole portion that maybe employed in the thin film magnetic head according to the presentinvention;

[0031]FIG. 6 illustrates yet another embodiment of the pole portion thatmay be employed in the thin film magnetic head according to the presentinvention

[0032]FIG. 7 is a perspective illustrating yet another embodiment of thepole portion that may be employed in the thin film magnetic headaccording to the present invention;

[0033]FIG. 8 is an enlarged frontal view of the pole portion illustratedin FIG. 7

[0034]FIG. 9 is a perspective illustrating another structure for thepole portion in the thin film magnetic head according to the presentinvention;

[0035]FIG. 10 is an enlarged frontal view of the pole portionillustrated in FIG. 9;

[0036]FIG. 11 is an enlarged plan view of the pole portion illustratedin FIG. 9;

[0037]FIG. 12 is a graph illustrating the relationship between the widthratio (W20/W21) and the standardized write magnetic field intensity; and

[0038]FIG. 13 is a graph illustrating the relationship between thereceding quantity ΔL and the standardized write magnetic fieldintensity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Referring to FIGS. 1 to 3, the combined type thin film magnetichead is provided with both a write element 2 and an MR read element 3.The write element 2 and the MR read element 3 are formed on a base body1 which is employed as a slider, with the read/write area located at anair bearing surface (hereafter referred to as an ABS) 10 of the basebody 1. The arrow “a” indicates the direction in which the magneticrecording medium rotates (the direction of airflow).

[0040] The write element 2, which is constituted of an inductive thinfilm magnetic transducer, is laminated on the MR read element 3.However, a structure in which the MR read element 3 is provided on thewrite element 2 may be adopted, instead.

[0041] The write element 2 is provided with a pole portion 20. As FIGS.2 and 3 illustrate, the pole portion 20 includes a first pole portion201, a second pole portion 202 and a gap film 23. The gap film 23 isprovided between the first pole portion 201 and the second pole portion202. The second pole portion 202 includes a third magnetic film 24 whichis provided adjacent to the gap film 23. As a result, the third magneticfilm 24 may be employed as a pole tip to set the head size, whichdetermines the width of the data tracks very small, determined by thewidth of the third magnetic film 24 so that the TPI capability can beimproved to achieve high density recording.

[0042] A fourth magnetic film 25 which is included in the second poleportion 202 is provided adjacent to the third magnetic film 24. By usingthe fourth magnetic film 25 as a yoke, the magnetic flux required forwrite operations can be supplied from the fourth magnetic film 25 to thethird magnetic film 24 constituting the pole tip. In other words,according to the present invention, a separate type thin film magnetichead in which a pole tip is provided separate from a yoke can beprovided.

[0043] In the embodiment, the first pole portion 201 includes a firstmagnetic film 21 and a second magnetic film 22. The second magnetic film22 is provided adjacent to the gap from 23, whereas the first magneticfilm 21 is provided adjacent to the second magnetic film 22.

[0044] The first magnetic film 21 to the fourth magnetic film 25 may beconstituted of permalloy under normal circumstances. The gap film 23 maybe constituted of a metal oxide such as Al₂O₃, SiO₂ or the like or itmay be constituted of a nitride such as AlN, BN, SiN or the like.Alternatively, it may be constituted of a conductive non-magneticmaterial such as Au, Cu, or NiP.

[0045] In the structure described above, the second magnetic film 22 andthe third magnetic film 24 of the four magnetic films, i.e., the firstmagnetic film 21 to the fourth magnetic film 25, are used as pole tipsso that the head size, which determines the width of the data tracks canbe set at a minute dimension determined by the widths W11 and W21 of thesecond magnetic film 22 and the third magnetic film 24 respectively,which achieves an improvement in the TPI capability to achieve highdensity recording. In the embodiment, the second magnetic film 22 isprovided projecting out above the first magnetic film 21, with the gapfilm 23 laminated on the second magnetic film 22. In addition, the thirdmagnetic film 24 is laminated on the gap film 23. The width W11 of asurface 220 of the second magnetic film 22 facing opposite the mediumand the width W21 at a surface 240 of the third magnetic film 24 facingopposite the medium are almost equal to each other.

[0046] At the same time, the first magnetic film 21 and the fourthmagnetic film 25 among the four magnetic films, i.e., the first magneticfilm 21 to the fourth magnetic film 25, extend rearward from the poleportion 20, with the portions extending rearward constituting yokes 211and 251 respectively. In this specification, “rearward” means thedirection opposite from the surfaces facing opposite the medium.

[0047] The yokes 211 and 251 constituted by the first magnetic film 21and the fourth magnetic film 25 respectively are linked with each otherat a rear linking portion 252, to complete a thin film magnetic circuit.A coil film 26 winds around the linking portion 252 in a coil, and thecoil film 26 is supported by an insulating film 27. The number of turnsand the number of layers of the coil film 26 are arbitrary. Thisstructure makes it possible to supply magnetic flux required for a writeoperation from the first magnetic film 21 and the forth magnetic film 25respectively constituting the yokes 211 and 251 to the second magneticfilm 22 and the third magnetic film 24 constituting pole tips. In otherwords, a separate magnetic pole type magnetic head in which poleportions are separated from the yokes can be achieved.

[0048] A surface 250 of the fourth magnetic film 25 facing opposite themedium includes a first side 251 adjacent to the third magnetic film 24and second first sides 252 and 253 extending outward from the two endsof the first side 251. The second sides 252 and 253 incline toward theopposite side of the third magnetic film 24 at an angle θ which is lessthan 90° relative to an extended line Bo of the first side 251. Throughthis structure, in which the edges of the fourth magnetic film 25 arecut off by the second sides 252 and 253, any recording bleed occurringdue to magnetic field leaking through the edges can be eliminated.

[0049] In the embodiment, the surface 250 of the fourth magnetic film 25facing opposite the medium is formed in a hexagonal shape having thefirst side 251, the second sides 252 and 253, lateral sides 254 and 255and an upper side 256. This hexagonal shape is maintained over almostthe entire length of the fourth magnetic film 25 at the pole portion 20.The width of the first side 251 is set at W21 which is the same as thelength of a first side (upper side) of the third magnetic film 24, andthe second sides 252 and 253 are provided at the two ends of the firstside 251. It is desirable that the second sides 252 and 253 incline atan angle equal to or greater than 45°.

[0050]FIG. 4 presents data that illustrate the relationship between theposition X (μm) and the leaked magnetic field Hx (k0e). As illustratedin FIG. 4, the position X is a position taken in the direction X of thetrack width, relative to the center 0 of the track width at the poleportion 20 (0 μm). In FIG. 4, characteristics curves (L0, L15, L30, L45,L60 and L75) achieved by using the angle of inclination θ (0°, 15°, 30°,45°, 60° and 75°) of the second sides 252 and 253 as a parameter arepresented.

[0051] As illustrated in FIG. 4, as the angle of inclination θincreases, the leaked magnetic field intensity at an edge E1 becomesreduced. This means that the leaked magnetic field at the edge E1 can beeffectively reduced by increasing the angle of inclination θ. However,problems arise as the angle of inclination θ becomes close to 90°, inthat edges appear again, in that the width W22 of the fourth magneticfilm 25 becomes equal to the width W21 of the third magnetic film 24 tocancel out the advantages (to be detailed later) achieved by projectingout the fourth magnetic film 25 relative to the third magnetic film 24,and the like. Thus, the angle of inclination θ of the second sides 252and 253 must be less than 90°.

[0052] Next, in consideration of application in combination with amagnetic recording medium (magnetic disk), it is desirable to ensurethat the leaked magnetic field at the edge E1 does not exceed 1.5 (k0e),since the magnetic recording medium typically as a coercivity ofapproximately 2.5 (k0e) and it is necessary to keep the leaked magneticfield intensity lower than the coercivity by approximately 1 (k0e) inorder to be able to disregard the influence of a write occurring due tothe magnetic field leaking through the edge E1 on the magnetic recordingmedium. FIG. 4 indicates that the angle of inclination θ at which theleaked magnetic field at the edge E1 does not exceed 1.5 (k0e) is 45° orgreater.

[0053] According to the present invention, the width W22 of the surface250 of the fourth magnetic film 25 facing opposite the medium is largerthan the width W21 of the surface 240 of the third magnetic film 24facing opposite the medium so that the fourth magnetic film 25 projectsout toward the outside relative to the third magnetic film 24 at bothsides in the widthwise direction. A width difference ΔW1 =(W22-W21)/2manifesting at both sides of the surfaces 240 and 250 facing oppositethe medium due to the difference between the width W22 and the width W21of the surface 240 of the third magnetic film 24 facing opposite themedium is equal to or less than 0.3 μm. In the range over which thewidth difference ΔW1 is equal to or less than 0.3 μm, the magnetic fieldleaking from the two ends of the fourth magnetic film 25 in itswidthwise direction can be reduced to a small value equal to or lessthan 2.0 (k0e).

[0054] The width W21 of the surface 240 of the third magnetic film 24facing opposite the medium can be set less than 2.0 μm to improve thetrack density. Such a small pole width can only be realized byconstituting the thin film magnetic head according to the presentinvention as a separate magnetic pole type and is a great advantage ofthe separate magnetic pole type. It is difficult to achieve such aminute pole width in a thin film magnetic head in the prior art of anon-separate magnetic pole type.

[0055] The surfaces 210, 220, 230, 240 and 250 all facing opposite themedium and belonging to the first magnetic film 21, the second magneticfilm 22, the gap film 23, the third magnetic film 24 and the fourthmagnetic film 25 respectively, constitute a single flat surface. Theflat surface constituted of the surfaces 210 to 250 facing opposite themedium constitutes a portion of the ABS 10. The second magnetic film 22,the gap film 23 and the third magnetic film 24 constitute a rear wallsurface which is essentially a single flat surface on the side oppositefrom the surfaces 220 to 240 facing opposite the medium. This rear wallsurface is essentially parallel to the ABS surface 10 constituted by thesurfaces facing opposite the medium.

[0056] The area around the first magnetic film 21, the third magneticfilm 24 and the gap film 23 is filled with a non-magnetic insulatingfilm 28 (see FIG. 1). The upper surface of the non-magnetic insulatingfilm 28 is flattened to form a flat surface that is essentially one andthe same surface as the surface of the third magnetic film 24. Thenon-magnetic insulating film 28 may be constituted of Al₂O₃, SiO₂ or thelike. Reference number 29 indicates a protective film which covers theentire structure and is constituted of Al₂O₃, SiO₂ or the like.

[0057] The second magnetic film 22 and the third magnetic film 24 arenormally constituted of Permalloy. In another mode, at least either thesecond magnetic film 22 or the third magnetic film 24 may be constitutedof a material having a higher saturation magnetic flux density comparedto that of Permalloy. In this case, satisfactory recording performanceis achieved even with a magnetic recording medium having a highcoercivity. A high saturation magnetic flux density material having ahigher saturation magnetic flux density compared to that of Permalloyshould be selected for this purpose. For instance, at least onesubstance selected from Fe—Co, Fe—M and Fe—Co—M may be used. In thiscontext, M represents at least one substance selected from N, C, B, Si,Al, Ti, Zr, Hf, Mo, Ta and Nb (all chemical symbols). The secondmagnetic film 22 and the third magnetic film 24 may both be constitutedof the high saturation magnetic flux density material described above oronly either one of them may be constituted of the high saturationmagnetic flux density material.

[0058] In addition, at least either the first magnetic film 21 or thefourth magnetic film 25 may be constituted of a material having a higherresistivity compared to that of Permalloy. This structure will reducethe eddy current loss compared to a structure employing Permalloy, whenthe frequency is increased at the write circuit. Specific examples ofthe high resistivity material include at least one substance selectedfrom Fe—Co amorphous, Fe—M—N, Fe—M—O, Fe—Co—M—N , Fe—Co—M—O and Fe—Co—N.In this context, M represents at least one substance selected from B,Si, Al, Ti, Zr, Hf, Mo, Ta and Nb (all chemical symbols). Both the firstmagnetic film 21 and the fourth magnetic film 25 may be constituted ofthe high resistivity material described above or only either one of themmay be constituted of the high resistivity material.

[0059] In FIG. 1, the MR read element 3 includes a first shield film 31,a second shield film 32, an MR element 33 and a lead conductor film 35.The first shield film 31 and the second shield film 32 are provided overa distance from each other, with the MR element 33 provided between thefirst shield film 31 and the second shield film 32. The second shieldfilm 32 constitutes the first magnetic film 21 of the write element 2. Anonmagnetic insulating film 34 is provided between the first shield film31 and the second shield film 32, with the MR element 33 and the leadconductor film 35 provided inside the non-magnetic insulating film 34.

[0060] The write element 2 is laminated onto the MR read element 3. Inthis structure, the second shield film 32 also functions as the firstmagnetic film 21 of the write element 2. Since the second magnetic film22 projects out over the first magnetic film 21, the width W11 of thesecond magnetic film 22 can be reduced to a great degree whilemaintaining the width of the second shield film 32 to dimensionsrequired to protect the MR read element 3.

[0061] According to the present invention, various types of inductivethin film magnetic transducers that have been proposed to date and thatwill be proposed in the future may be employed to constitute the writeelement 2. In addition, various types of read elements that have beenproposed to date and that will be proposed in the future including thoseusing a magnetic anisotropic magnetoresistive film such as a Permalloyfilm and those utilizing the giant magnetoresistance effect by employinga spin valve film, a tunnel junction effect film or the like, may beused to constitute the MR read element 3. The write element 2 and the MRread element 3 are mounted on a slider. The slider may be provided withone or more rails, or a slider without rails may be employed.

[0062] Next, in reference to FIGS. 5 to 10, other embodiments of thethin film magnetic head according to the present invention areexplained. First, in the embodiment illustrated in FIG. 5, the surface250 of the fourth magnetic film 25 facing opposite the medium is formedin a trapezoidal shape with the second sides 252 and 253 that arecontinuous to the two ends of the first side 251 extending to the upperside 256. The lateral sides 254 and 255 in the embodiment illustrated inFIGS. 2 and 3 are not present.

[0063] In the embodiment illustrated in FIG. 6, the lateral side 255continuous to the second sides 252 and the lateral side 254 continuousto the second sides 253, too, incline at an angle less than 90° relativeto the first side 251.

[0064] In the embodiment illustrated in FIGS. 7 and 8, while the surface250 of the fourth magnetic film 25 facing opposite the medium is formedin a hexagonal shape, the hexagonal shape ends in the middle area towardthe rear from the surface 250 at the fourth magnetic film 25 facingopposite the medium.

[0065]FIG. 9 is a perspective illustrating another structure for thepole portion of the thin film magnetic head according to the presentinvention, FIG. 10 is an enlarged frontal view of the pole portionsillustrated in FIG. 9 and FIG. 11 is an enlarged plan view of the poleportions illustrated in FIG. 9. This embodiment is characterized in thatthe third magnetic film 24 has a width W20 which is larger than thewidth W21 at the surface 240 facing opposite the medium, at the positionreceding from the surface 240 facing opposite the medium. Through thisstructure, magnetic saturation can be prevented from occurring at thepole tip constituted of the third magnetic film 24 to preventdegradation of the recording magnetic field pitch and recording bleedoccurring due to leaked magnetic field.

[0066] It is desirable that the width ratio (W20/W21) of the width W20and the width W21 satisfy 1.2≦(W20/W21)≦1.8. Within this range, a highdegree of write magnetic field intensity can be achieved, whereas thewrite magnetic field intensity is reduced remarkably outside this range.

[0067] In addition, the receding quantity ΔL representing the distancefrom the surface facing opposite the medium to the position at which thewidth is increased to the width W20 be within a range of 0.2 to 0.8 μm.Within this range, a sufficient write magnetic field intensity can beassured for magnetic recording, whereas the write magnetic fieldintensity is drastically reduced outside this range.

[0068]FIG. 12 presents data illustrating the relationship between thewidth ratio (W20/W21) and the standardized write magnetic fieldintensity. The data presented in FIG. 12 were obtained with the recedingquantity ΔL set at 0.6 μm. The data in FIG. 12 indicate that writemagnetic field intensity characteristics that achieve an upward archingcurve are obtained within the range of 1.2≦(W20/W21)≦1.8 to assure ahigh write magnetic field intensity. As the width ratio (W20/W21)becomes less than 1.2, the standardized magnetic field intensity becomesdrastically reduced. As the width ratio (W20/W21) becomes larger than1.8, the write magnetic field intensity becomes reduced remarkably, too.Although not shown, data indicating a similar tendency to that in FIG.12 were obtained with the receding quantity ΔL set at 0.2 μm and 0.8 μm.

[0069]FIG. 13 presents data illustrating the relationship between thereceding quantity ΔL and the standardized write magnetic fieldintensity. The data presented in FIG. 13 were obtained by setting thewidth ratio (W20/W21) at 1.4. The data in FIG. 13 indicate that writemagnetic field intensity characteristics that achieve an upward archingcurve are obtained within the range of 0.2≦Δ≦0.8 to assure a high writemagnetic field intensity. As the receding quantity ΔL becomes less than0.2, the standardized magnetic field intensity becomes drasticallyreduced. As the receding quantity ΔL becomes larger than 0.8, the writemagnetic field intensity becomes reduced remarkably, too. Although notshown, data indicating a similar tendency to that in FIG. 13 wereobtained with the width ratio (W20/W21) set at 1.2 and 1.8.

[0070] While the invention has been particularly shown and describedwith respect to preferred embodiments thereof by referring to theattached drawings, the present invention is not limited to theseexamples and it will be understood by those skilled in the art thatvarious changes in form and detail may be made therein without departingfrom the spirit, scope and teaching of the invention.

What is claimed is:
 1. A thin film magnetic head having at least onewrite element comprising a first pole portion, a second pole portion anda gap film; said gap film being provided between said first pole portionand said second pole portion; said second pole portion having a thirdmagnetic film and a fourth magnetic film; said third magnetic film beingprovided adjacent to said gap film; and said fourth magnetic film beingprovided adjacent to said third magnetic film; wherein a surface of saidfourth magnetic film that faces opposite a medium includes a first sideand second sides; said first side is provided adjacent to said thirdmagnetic film; said second sides extend outward from at least one end ofsaid first side and incline toward a side opposite from said thirdmagnetic film at an angle smaller than 90° , relative to an extendedline of said first side.
 2. The thin film magnetic head of claim 1 ,wherein: said first pole portion includes a first magnetic film and asecond magnetic film, with said second magnetic film provided adjacentto said gap film and said first magnetic film provided adjacent to saidsecond magnetic film.
 3. The thin film magnetic head of claim 1 ,wherein: said second sides are provided at two ends of said first side.4. The thin film magnetic head of claim 1 , wherein said second sidesincline at an angle equal to or larger than 45°.
 5. The thin filmmagnetic head of claim 3 , wherein: said surface of said fourth magneticfilm facing opposite said medium is formed in a hexagonal shape thatincludes two second sides.
 6. The thin film magnetic head of claim 3 ,wherein: said surface of said fourth magnetic film facing opposite saidmedium is formed in a quadrangular shape that includes two second sides.7. The thin film magnetic head of claim 1 , further comprising an MRread element that including a first shield film, a second shield filmand an MR element; said MR element being provided between said firstshield film and said second shield film; and said second shield filmconstituting said first magnetic film of said write element.